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.TH BSD_SIGNAL 3C "May 13, 2017"
.SH NAME
bsd_signal \- simplified signal facilities
.SH SYNOPSIS
.LP
.nf
#include <signal.h>

\fBvoid\fR (\fB*bsd_signal(int\fR \fIsig\fR, \fBvoid\fR (*\fIfunc\fR)(\fBint\fR)))(\fBint\fR);
.fi

.SH DESCRIPTION
.LP
The \fBbsd_signal()\fR function provides a partially compatible interface for
programs written to historical system interfaces (see \fBUSAGE\fR below).
.sp
.LP
The function call \fBbsd_signal\fR(\fIsig\fR, \fIfunc\fR) has an effect as if
implemented as:
.sp
.in +2
.nf
void (*bsd_signal(int sig, void (*func)\|(int)))\|(int)
{
     struct sigaction act, oact;

     act.sa_handler = \fIfunc\fR;
     act.sa_flags = SA_RESTART;
     sigemptyset(&act.sa_mask);
     sigaddset(&act.sa_mask, \fIsig\fR);
     if (sigaction(\fIsig\fR, &act, &oact) == \(mi1)
          return(\fBSIG_ERR\fR);
     return(oact.sa_handler);
}
.fi
.in -2

.sp
.LP
The handler function should be declared:
.sp
.in +2
.nf
void handler(int \fIsig\fR);
.fi
.in -2

.sp
.LP
where \fIsig\fR is the signal number.  The behavior is undefined if \fIfunc\fR
is a function that takes more than one argument, or an argument of a different
type.
.SH RETURN VALUES
.LP
Upon successful completion, \fBbsd_signal()\fR returns the previous action for
\fIsig\fR. Otherwise, \fBSIG_ERR\fR is returned and \fBerrno\fR is set to
indicate the error.
.SH ERRORS
.LP
Refer to \fBsigaction\fR(2).
.SH USAGE
.LP
This function is a direct replacement for the \fBBSD\fR \fBsignal()\fR
function for simple applications that are installing a single-argument signal
handler function.  If a \fBBSD\fR signal handler function is being installed
that expects more than one argument, the application has to be modified to use
\fBsigaction\fR(2). The \fBbsd_signal()\fR function differs from the \fBBSD\fR
\fBsignal()\fR in that the \fBSA_RESTART\fR flag is set and the
\fBSA_RESETHAND\fR will be clear when \fBbsd_signal()\fR is used.  The state of
these flags is not specified for the \fBBSD\fR \fBsignal()\fR.
.SH ATTRIBUTES
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.LP
.BR sigaction (2),
.BR sigaddset (3C),
.BR sigemptyset (3C),
.BR attributes (7),
.BR standards (7)
